should I get a 5g and put diego and my adf in it (so the platys leave him alone (they follow him like he's their god and he hates it)

This part made me chuckle cus my 3 Cardinal Tetras do the same thing with Speedbump, my betta. They think he is like god and so they follow him around like you are describing. Speedbump is pretty tolerant and if he has enough he will kinda chase one away and the 3 Cardinals have kinda calmed down and realized their beloved leader isn't going anywhere so they are giving him some more space now.

But if it is affecting your Betta in a negative way maybe you should consider moving him if you have the space, money and means to do so.

I dunno about getting females though, maybe someone else can help on that one.